RFR: 8224666: Parallel GC: Use WorkGang (8: obsolete and remove flags)

[Leo Korinth]

Hi,

Here is the eighth and last patch that removes gcTaskManager and uses
the WorkGang abstraction instead.

This patch removes and obsoletes two product flags.

BindGCTaskThreadsToCPUs is used to run threads pinned on specific
CPUs. Only implemented on Solaris and seems mostly unused.

UseGCTaskAffinity is used to take tasks with a certain thread
affinity; it does not work and should have been obsoleted since (at
least) JDK-8138707.

The code tries to obsolete BindGCTaskThreadsToCPUs and UseGCTaskAffinity
in JDK 13. Push the removal _before_ next LTS(17); proposed removal is 
thus 16.


Enhancement:
   https://bugs.openjdk.java.net/browse/JDK-8224666

Webrev:
 
http://cr.openjdk.java.net/~lkorinth/workgang/0/_8224666-Parallel-GC-Use-WorkGang-8-obsolete-and-remove-flags/
   http://cr.openjdk.java.net/~lkorinth/workgang/0/all/

Testing (on the whole patch series):
   mach5 remote-build-and-test --build-profiles 
linux-x64,linux-x64-debug,macosx-x64,solaris-sparcv9,windows-x64 --test 
open/test/hotspot/jtreg/:hotspot_gc -a -XX:+UseParallelGC
   gc test suite

Thanks,
Leo